Patch to prevent "amount" column from being added to cart table when there are no donation products in the cart

This patch checks to see if there are any donation products in the cart before adding the "Amount" column to the cart review table. I created this patch because having the "Amount" column in the cart table is confusing for the customer when there are no donation products in their cart.

This patch was applied against 6.x-2.x-dev. I've tested it with 6.x-2.0-beta3 and it seems to be working fine.

This is my first contributed patch, so please feel free to modify it if you find a better solution.

I'll explain the changes in case anyone runs into difficulty applying the patch.

In "uc_donation.module", I replaced lines 111 to 123:

<?php
if ($form_id == 'uc_cart_view_form') {
  $form['items']['#columns']['donate_amount'] = array('cell' => t('Amount'), 'weight' => 3);
  $form['items']['#columns']['qty']['weight']++;
  $form['items']['#columns']['total']['weight']++;
  $form['#validate'][] = 'uc_donation_cart_view_validate';

  // Add spacer to regular products for amount column
  foreach (element_children($form['items']) as $item) {
    if (isset($form['items'][$item]['module']) && $form['items'][$item]['module']['#value'] != 'uc_donation') {
      $form['items'][$item]['desc']['#cell_attributes']['colspan'] = '2';
    }
  }
}
?>

with the following:

<?php
if ($form_id == 'uc_cart_view_form') {
  // Determine if a donation product has been added to the cart
  $donation_in_cart = FALSE;
  foreach (element_children($form['items']) as $item) {
    if (isset($form['items'][$item]['module']) && $form['items'][$item]['module']['#value'] == 'uc_donation') {
      $donation_in_cart = TRUE;
    }
  }
  // If there is a donation product in the cart, alter the table
  if ($donation_in_cart) {
    $form['items']['#columns']['donate_amount'] = array('cell' => t('Amount'), 'weight' => 3);
    $form['items']['#columns']['qty']['weight']++;
    $form['items']['#columns']['total']['weight']++;
    // Add spacer to regular products for amount column
    foreach (element_children($form['items']) as $item) {
      if (isset($form['items'][$item]['module']) && $form['items'][$item]['module']['#value'] != 'uc_donation') {
        $form['items'][$item]['desc']['#cell_attributes']['colspan'] = '2';
      }
    }
  }
  $form['#validate'][] = 'uc_donation_cart_view_validate';
}
?>